Transmission clutch control



Jan. 23, 1 962 H. L. LAsLEY TRANSMISSION CLUTCH CONTROL Filed Deo. '7,1959 Nw .IJ

N N k United States Patent @thee l'iM Patented Jam. 23, i952 3,017,974TRANSMISSION CLUTCH CONTROL Harold L. Lasley, West Des Moines, Iowa,assigner to General Motors Corporation, Detroit, Mich., a corporation ofDelaware Filed Dec. 7, 1959, Ser. No. 857,793 Claims. (Cl. 192-4) Thisinvention relates to automotive vehicles equipped with liuid pressureoperated braking and power transmission systems including means forautomatically disengaging the transmission upon the application ofbraking pressure in the brake system and, more particularly, is directedto an improvement in a system of this type disclosed in the copendingUnited States application Serial No. 812,268, filed May 1l, 1959, in thename of Ralph I. Bernotas.

This invention is directed particularly to that class of heavy dutyvehicles such as is found in the earth working trade and which, duringordinary operation, -are subjected to quite frequent braking action. Forexample, a front end loader is a vehicle which carries at its front enda suitable linkage supporting a loader bucket. Through such means ashydraulic rams or the like, such a loader vehicle is adapted to dig,transport and dump loads. Such vehicles typically include fluid powertransmissions utilizing a torque converter or other fluid coupling and aplurality of fluid operated clutches or brakes which may be selectivelyengaged by a manually operated selector valve to select a particulargear range in the transmission. Naturally, such vehicles also include asuitable fluid pressure operated braking system. Inasmuch as suchvehicles are subjected to repeated braking, it is desirable, for severalreasons, to provide some means for automatically disengaging thetransmission upon application of the brake.

In the lirst instance, power is obviously wasted if drive continues tobe transmitted through a vehicle transmission while the vehicle is beingbraked. With reference particularly to a front end loader or othervehicles of this type, the operator is normally quite intent on theproper operation of the device or devices with which the vehicle isequipped, and it is not readily convenient for him to de-clutch orinterrupt drive through the transmission each time he applies hisbrakes.

Therefore, it is a principal object and feature of this invention toprovide means for automatically disengaging a fluid power transmissionin response to the application of braking pressure in a vehicle brakingsystem.

Quite frequently, the operator of such vehicles to which reference hasbeen made will repeatedly apply slight braking pressure to the vehicleto enable the latter to perform as efficiently as possible. For example,with reference to a front end loader, the vehicle operator may drive upto a heaped pile of material with his bucket in the loading position. Atthis point, he may wish to inch into the material in an effort to obtaina loaded bucket, thereby requiring repeated braking efforts. In such asituation, it is not too feasible to require the vehicle operator torepeatedly manually disengage and engage the transmission as he brakesthe vehicle. Additionally, the particular operation may be such that thevehicle operator does not wish to disengage the transmission inasmuch ashe is applying only slight braking pressure and does not wish to Waitfor the transmission to automatically become engaged `again upon releaseof the braking pressure.

Therefore, it is yet another object and feature of this invention toprovide a means for automatically disengaging a fluid power transmissionin response to the application of a predetermined high amount of brakingpressure in the brake system such as substantially full-stop brakingpressure.

In a system of this type in which the transmission is to be disengagedin response to full-stop or a predetermined amount of brake pressure, itis equally desirable that the transmission be adapted for promptrcs-engagement when the brake pressure falls below such full-stoppressure. For example, if the vehicle is braked to a full stop on anincline thereby resulting in transmission disengagement, 'a conditionmay follow in which brake pressure is reduced to a point below full-stopbut suliiciently high to hold the vehicle on the incline. Thereafter, ifbrake pressure is further reduced to release the Vehicle for travel, thevehicle may roll a considerable distance depending on the nature of theincline before the transmission re-engages.

It is, therefore, another object and feature of this invention toprovide means for automatically re-engaging the transmission afterfull-stop braking in response to brake pressure falling below thefull-stop or otherwise predetermined brake pressure.

As is well known, clutch or brake plates are employed in such a fluidpower transmission aforementioned in order to select a particular gearrange through the transmission. As is equally well known, rapidengagement and disengagement of the clutch plates is quite importantsince these plates deteriorate rapidly if subjected to repeated slippingunder the conditio-ns of operation to which they are subjected.

Therefore, it is yet another object and feature of this invention toprovide an automatically operable transmission disengaging means whichwill operate rapidly to engage and `disengage the transmission Withoutundue slipping of the clutch or brake plates aforementioned.

In general, these and other objects of this invention are attained inthe combination of a vehicular braking system and power transmissionWith fluid-operated overcontrol means communicating the brake system tothe power transmission system so as to disengage the latterautomatically in response to a predetermined substantially full-stopbraking pressure. To this end, the transmission includes a de-clutchingor other drive interrupting valve having inlet and pressure portsadapted to communicate the transmission fluid power source to theengageable and disengageable clutch plates or other drive means throughwhich drive is conducted in the transmission. The valve also includes anexhaust port for dumping the tiuid from the fluid-actuated drive means.The valve is operated in response to braking pressure in the brakesystem to move the valve from a first position communieating the drivemeans with the transmission fluid source to a second positioninterrupting flow of fluid from the transmission source Iand dumping thefluid-operated drive means to tank. Check valve means is provided in theconnection between the braking system and the overcontrol valve toinsure that the latter s operated rapidly and only upon the achievementof a predetermined relatively high rbraking pressure in the brake systemso as to insure that the transmission is not disengaged when relativelyslight braking pressures are applied. Furthermore, a bleed connection ismade to the over-control valve between the latter and the aforementionedcheck valve so that the pressure acting on the over-control valve isbled olf rapidly when the pressure in the braking system falls below thesetting of the check valve.

These and other objects of this invention will become more apparenthereinafter as the description of the invention proceeds, and in whichreference is made to the drawing illustrating the invention. In order tofacilitate an understanding of the invention, wherever possibleconventional components and those readily commercially available areshown essentially diagrammatically or schematically in the drawing.

Referring now to the drawing, there is. illustrated essentiallyschematically a brake system comprising a tank 2 for hydraulic fluidfrom which the pump 4 draws to supply iiuid under pressure to theaccumulator 6 and through the conduit S to the brake treadle valve lwhich is op-erated in response to depression of the brake pedal 12. The-return line to the tank is indicated at i4. The pressure port of thebrake valve 10 is connected tothe conduit i6 which is connected throughthe line 1S to the front and rear brakes which are of conventionalconstruction including the iiuid pressure-actuated brake cylinders ormotors 20.

The iiuid power transmission system includes a source of hydraulic uid22 which is supplied und-er pressure by the pump 24 to the conduit 26and branch conduit 28. The branch conduit 28 supplies fluid underpressure to the transmsison torque converter and forward and reverseclutch, while the main conduit 26 supplies fluid under pressure to theover-control or transmission cut-off valve 30. A conduit 32 connects theover-control valve 30 to the range selector clutch valve 33 which is ofconventional construction and is adapted to be manually selectivelyshifted to supply fluid under pressure through different conduits 34, 36and 38, respectively, supplying fluid motor actuated disc clutches orbrakes to select a first, second or third gear range through thetransmission.

It will be seen that the over-control valve 30 includes a valve body 40having an internal bore 42 therethrough. An annular inlet port 44communicates with the pressure conduit 26, while a similar pressureoutlet port 46 communicates with the range selector clutch valve 33thro-ugh the conduit 32. Each of the exhaust ports 4S, 50 and 52 areadapted to return fluid to the tank or sum-p 22. It will be noted thatthe end exhaust ports 48 and 52 are disposed at either end of the valvebody bore 42 so as to prevent any adverse pressure build-up on the valvespool to be described.

The valve spool 54 is axially reciprocably mounted within the valve bodybore and includes a piston head 56 at one end thereof and a pair ofaxially spaced valve lands 5S and 60. rl`he valve land 60 is in the formof a cup to define a seat for a spring 62 guided about a coaxial stud 64secured within the valve body. The pressure of th-e spring 62 normallydisposes the valve spool in the position shown in the drawing, and inwhich position the inlet port 44 and pressure port 46 are placed incommunication with each other, while the valve land 60 closes theexhaust po-rt 50. When the valve spool is shifted to the right in amanner to be described, the valve land 5S closes the inlet port 44 andthe valve land 60 is shifted to the right until it abuts the stud 64while opening 4the exhaust port 50 for communication with the pressureoutlet port 46. In this shifted position, fluid under pressure -is nolonger supplied from the pump to the selected clutch, while the latteris dumped to tank thereby disengaging the transmission.

In order to shift the spool valve S4 in response to braking pressure inthe brake system, the conduit 18 is connected to `the valve body 40 soas to communicate braking pressure to the end of the piston 56 on thevalve spool. The conduit 18 includes the one-way spring-loaded ballcheck valve 7@ -which is adapted to be moved from its seat in responseto a predetermined braking pressure in the brake system to supply iiuidto the piston end olf the valve spool to shift the latter to the rightas aforedescribed. Upon release of the predetermined braking pressure,return fluid from the control valve 30 may pass through conduit 72connecting line 18 downstream of check valve 70 to the return line 14. Afitting including a small restriction or orifice 74 is connected in theconduit 72.

Referring now to the operation of the mechanism disclosed, it may beassumed that the vehicle operator has adjusted the selector valve 33 toplace the transmission in a particular gear range, and is travellingalong without applying any braking effort. At this time, the overcotnrolor clutch valve 30 is `in the position shown in which fluid from thepump 22 may pass through the inlet port 44 to the outlet port 46 andthrough the selector valve to apply the selected clutch. lf the operatorshould now apply a predetermined braking pressure to the pedal l2, thecheck valve 70 will open to permit fluid under pressure in the line 18to rapidly reciprocate the valve spool 54 to the right. As a result,`the valve land 53 interrupts `communication between the inlet port 44and outlet port 46, valve land 60 opens exhaust port 50 and fluidpressure is dumped from port 46 through the exhaust port 50 to tank. Assoon as the predetermined braking pressure in the braking system isrelieved, pressure will drop in the conduit 18, the check valve 70 willimmediately close and return uid will flow through the conduit 72 andorifice 74. As a result, the spring 62 rapidly shifts the valve spool 54back to the position shown in the drawing, thereby again permitting theiiow of fluid under pressure through the valve 30 to reapply theselected clutch and place the transmission back in gear. Shifting of thevalve spool 54 is quite rapid in either direction, thereby providingrapid engagement and disengage` :ment of the selected clutch andavoiding undue slipping of the latter.

As aforementioned, there will be times in which the operator may wish toapply a slight braking pressure without disengaging his transmisison.Therefore, the spring-loaded check valve 70 is set to open at somepredetermined relatively high braking pressure in the brake system. Forexample, in one preferred application of the invention, the brake linepressure in the conduit 18 reaches a maximum of about 1,000 p.s.i. Thecheck valve 70 is accordingly set to open at approximately 700 p.s.i.The 700 p.s.i. setting for the valve 70 corresponds to the applicationof a braking pressure o-f a significant nature which indicates that theoperator wishes to fully stop the machine. i

Finally, it will be noted that the aforedescribed construction avoidsthe possibly dangerous condition of the vehicle rolling on an inclineupon release of the brakes. ln this regard, and again referring to thepreferred ernbodiment, some selected low pressure such as onlyapproximately p.s.i. pressure is required to shift spool 54 to thetransmission disengage position while the openclose transition point ofvalve 70 is at a pressure of approximately 700 p.s.i. to insuretransmisison disengagement at only such higher pressure. Thus, whenfullstop braking pressure is released so that the pressure in the brakesystem is less than the setting of valve 70, the latter closes to stopthe flow of fluid to over-control valve 30. Immediately, the uidpressure acting on valve 30 is bled through conduit 72 to permit rapidshifting of spool 54 to the position shown in the drawing and thetransmission is re-engaged. Therefore, in a situation in which thevehicle is brought to a full stop on an incline and then the pressure inthe braking system is adjusted to a value less than the setting of valve70 but sufficient to hold the vehicle stationary, the bleeding actionaforedescribed insures that the transmission will be re-engaged to holdthe vehicle on the incline when the brakes are released. The diameter oforifice 74 is so selected in any given installation so as to be smallenough in relation to the capacity of pump 4 to insure that fluid willbe available for operating the over-control valve 30 although some uidwill be bled through conduit 72, while being large enough for rapidbleeding of valve 30 to re-engage the transmission as aforedescribed.

While but one form of the invention has been selected for a descriptionthereof, other forms will be apparent to those skilled in the art.Therefore, the embodiment shown in the drawing is merely forillustrative purposes, and is not intended to limit the scope of theinvention which is defined by the claims which follow.

I claim:

1. In a vehicle, the combination comprising fluid pressure-operatedvehicle brakes, a fluid pressure brake system including means forsupplying iluid under pressure to said brakes to engage the latter, apower transmission including fluid pressure-actuated drive meansengageable to conduct drive through said transmission and disengageableto interrupt drive therethrough, a fluid pressure transmission systemfor supplying fluid under pressure to said drive means, a fluidpressure-operated control valve in said transmission system controllingthe flow of fluid through the latter to said drive means and having afirst position permitting ow of fluid through said transmission systemand a second position interrupting said flow, means connecting saidbrake system to said control valve to adjust the latter from said rstposition to said second position in response to the application of apredetermined braking pressure in said brake system in eX- cess of thepressure required to adjust said control valve from said first positionto said second position, and means connected to said control valve forexhausting fluid pressure from and automatically shifting the latter tosaid first position at any time that the pressure in said brake systemis less than said predetermined pressure.

2. in a vehicle, the combination comprising iiuid pressure-operatedvehicle brakes, a fluid pressure brake sys- `tem including means forsupplying uid under pressure to said brakes to engage the latter, apower transmission including Huid pressure-actuated drive meansengageable to conduct drive through said transmission and disengageableto interrupt drive therethrough, a fluid pressure transmission systemfor supplying fluid under pressure to said drive means, a fluidpressure-operated control valve in said transmission system controllingthe ilow of fluid through the latter to said drive means and having afirst position permitting ilow of fluid through said transmission systemand a second position interrupting said iiow, means connecting saidbrake system to said control valve to adjust the latter from said irstposition to said second position in response to the application ofsubstantially full braking pressure in said brake system, and meansconnected to said control valve for exhausting tluid pressure from andautomatically shifting the latter to said first position at `any timethat the pressure in said brake system is less than said substantiallyfull braking pressure.

3. In a vehicle, the combination comprising fluid pressure-operatedvehicle brakes, a uid pressure brake system including means forsupplying fluid under pressure to said brakes to engage the latter, apower transmission including fluid pressure-actuated drive meansengageable to conduct drive through said transmission and disengageableto interrupt drive therethrough, a fluid pressure transmission systemsupplying iiuid under pressure to said drive means, a fluidpressure-operated control valve in said transmission system controllingthe flow of fluid through the latter to said drive means and having afirst position permitting dow of fluid through said transmission systemand a second position interrupting said fiow, means including a checkvalve connecting said brake system to said control valve to `adjust thelatter from said rst position to said second position in response to theapplication of substantially full braking pressure in said brake system,and means connected to said control valve for exhausting iiuid from thelatter to permit automatic movement thereof to said rst position at anytime that the pressure in said brake system is less than said fullbraking pressure.

4. In a vehicle, the combination comprising iiuid pressure-operatedvehicle brakes, a fluid pressure brake system including means forsupplying uid under pressure to said brakes to engage the latter, apower transmission including iluid pressure-actuated drive meansselectively engageable to conduct drive through said transmission anddisengageable to interrupt drive therethrough, a fluid pressuretransmission system for supplying lluid under pressure to said drivemeans, a fluid pressure-operated control valve in said transmissionsystem controlling the iiow of fluid through the latter to said drivemeans `and having la iirst position permitting flow of lluid throughsaid transmission system and a second position interrupting said ilow, apressure supply conduit including check valve means connecting saidbrake system to said control valve to adjust the latter from said firstposition to said second position in response to the application ofsubstantially full braking pressure in said brake system, and a bleedconduit connected to said supply conduit between said check valve meansand control valve for bleeding fluid from the latter to permit`automatic movement thereof to said first position at any time that thepressure in said brake system is less than said full braking pressure.

5. In a vehicle, the combination comprising fluid pressure-operatedvehicle brakes, a fluid pressure brake system including means forsupplying fluid under pressure to said brakes to engage the latter, apower transmission including fluid pressure-actuated drive meansselectively engageable to conduct drive through said transmission anddisengageable to interrupt drive therethrough, a fluid pressuretransmission system including manually operable selector valve means forselectively supplying and interrupting the ilow of liuid under pressureto said drive means to engage and disengage the latter, a liuidpressureoperate-d control valve in said transmission system controllingt'ne ilow of fluid through the latter to said drive means irrespectiveof the position of said selector valve means and having a first positionpermitting flow of fluid through said transmission system and a secondposition interrupting said iiow, a pressure supply conduit includingcheck valve means connecting said brake system to said control valve toadjust the latter from said first position to said second position inresponse to the application of a predetermined braking pressure in saidbrake system, and a bleed conduit connected to said supply conduitbetween said check valve means and control valve for bleeding fluid fromthe latter to permit automatic movement thereof to said lirst positionat any time that the pressure in said brake system is less than saidpredetermined pressure.

6. In a vehicle, the combination comprising a fluid pressure-operatedbrake system including fluid pressureactuated brake means, `a brakefluid circuit connected to said brake means, and a manually operablebrake valve in said circuit selectively controlling the amount ofbraking pressure supplied to said brake means, a power transmissionincluding iiuid pressure actuated drive means selectively engageable toconduct drive through said transmission, `a transmission iiuid circuitconnected to said drive means; means for automatically disengaging saiddrive means in response to the application of substantially full brakingpressure in said brake system, said means comprising a control valve insaid transmission circuit, spring means urging said valve to a firstposition permitting the flow of fluid under pressure to said drivemeans, and being yieldable upon shifting of said valve to a secondposition to exhaust fluid pressure from said drive means, 4a supplyconduit communicating braking system pressure `to said valve inopposition to said spring means, check valve means in said conduitpermitting the ow of fluid under pressure through said conduit to saidvalve only at substantially full braking pressure in said brake system,and a bleed conduit for bleeding fluid from said control valve to permitthe latter to shift to said rst position at `any pressure in saidbraking system less than said full braking pressure.

7. In `a Vehicle, the combination comprising a fluid pressure-operatedbrake system including a source of fluid under pressure and fluidpressure-.actuated brake means, a brake fluid circuit connected to saidbrake means, and la manually operable brake valve in said circuitselectively controlling the amount of braking pressure supplied to saidbrake means; a power transmission including fluid pressure-actuateddrive means selectively engageable to conduct drive through saidtransmission,

a transmission fluid circuit connected to said drive means; means forautomatically disengaging said drive means in response to theapplication of substantially full braking pressure in said brake system,saidmeans comprising a shiftable control Valve in said transmissioncircuit, spring means urging said valve to a first position permittingflow of fluid under pressure to said drive means, and being yieldableupon shifting of said valve to a second position to exhaust fluidpressure from said drive means, `a supply conduit communicating brakingsystem pressure to said valve in opposition to said spring means, aoneway spring loaded `check valve in said conduit permitting the flow ofiluid under pressure through said conduit to said valve only atsubstantially full braking pressure in said brake system, 4and a bleedconduit connected between said control valve and said source andbypassing said check valve for bleeding fluid from said control valve topermit the latter to shift to said first position at any pressure insaid braking system less than said liull braking pressure.

8. In a vehicle, the combination comprising a fluid pressure-operatedbrake system including a source of liu-id under pressure, fluidpressure-actuated brake means, a brake circuit connecting said source tosaid brake means, anda manually operable brake valve in said circuitselectively controlling the amount of braking pressure supplied to saidbrake means; a power transmission including drive means selectivelyengageable to conduit drive through said transmission, fluidpressure-operated motor means controlling engagement of said drivemeans, a source or" fluid under pressure, a transmission circuitconnecting said source to said motor means; means for automaticallydisengaging said drive means in response to the `application ofsubstantially full braking pressure in said brake system, said meanscomprising valve means in said transmission circuit, said valve meanscomprising an inlet port connected to said transmission fluid source, apressure outlet port connected to said motor means, an exhaust port, almovable valve member controlling flow of Huid between said ports,spring means urging said valve member to a first position communicatingsaid inlet and pressure ports and closing said exhaust port, and beingyieldable upon shifting of said valve member to a second positioncommunicating said pressure and exhaust ports, a first conduitcommunicating braking system pressure to said valve member in oppositionto said spring means, `check valve means in said conduit permitting theflow of fluid under pressure through said conduit to said valve memberonly at substantially full braking pressure in said brake system, and asecond conduit including a small orifice connected between said controlvalve and said fluid source of said brake system for bleeding fluid fromsaid control valve to shift said valve member to said first position atany pressure in said brake circuit less than said full braking pressure.

9. ln a vehicle, the combination comprising fluid pressure-operatedvehicle brakes, a liuid pressure brake system including means forsupplying fluid under pressure to said brakes to engage the latter, apower transmission including fluid pressure-actuated drive meansengageable to conduct drive through said transmission and disengagelableto interrupt drive therethrough, a fluid pressure transmission systemfor supplying liuid under pressure to said drive means, a fluidpressure-operated control valve in said transmission system controllingthe flow of fluid through the latter to said drive means and having iafirst position permitting flow of lluid through said transmission systemand a second position interrupting said flow, means including a firstconduit connecting said brake system to said control valve to adjust4the latter from said first position to said second position in responseto the application of a predetermined braking pressure in said brakesystem, and means including a second conduit connected to said firstconduit for exhausting fluid pressure from said control valve to shiftthe latter automatically to said first position at any time that thebraking pressure in said brake system is less than said predeterminedpressure.

l0. lin a vehicle, the `combination comprising fluid pressure-operatedvehicle brakes, a fluid pressure brake system including means forsupplying fluid under pressure to said brakes to engage the latter7 apower transmission including fluid pressure-actuated drive meansengageable to conduit drive through said transmission and disengageableto interrupt drive therethrough, a iiuid pressure transmission systemfor supplying fluid under pressure to said drive means, la fluidpressure-operated control valve in said transmission system controllingthe flow of fluid through the latter to said drive means iand having lafirst position permitting flow of fluid through said transmission systemand a second position interrupting said flow, means including a firstconduit connecting said brake system to said control valve to adjust thelatter from said first position to said second position in response tothe application of a predetermined braking pressure in said brake systemin excess of the pressure required to adiust said control valve fromsaid first position to said Second position, and means including asecond conduit connected to said r-st conduit for exhausting fluidpressure from said control valve to shift the latter iautomatically tosaid first position lat any time that the pressure in said brake systemis less than said predetermined pressure.

References Cited in the file of this patent UNITED STATES PATENTS UNITE)STATES PATENT FFCE CERTIFICATE OF CRBTN Patent Neo 30179'z4 l y January23 1962 Harold Lo Lesley y It is hereby certified that error appears inthe above numbered patentrequring correction and that lthe said LettersPatent should read as "corrected below.

Column TV line 28,I and celumn 87 line 29q for "conduiU each occurrenceIread conduct, mo

Signed and sealed this 8th day of May 1962.

(SEAL) Attest:

ERNEST `W `SWIDEB. DAVID L. LADD Attesting Officer l Commissioner ofPatents

